Re: [Paddlewise] Fin Fan Article

From: John Winters <735769_at_ican.net>
Date: Fri, 25 Dec 1998 10:45:17 -0500
Steve wrote;

>Isn't the aft most portion of a kayak's keelson referred to as a skeg?
Some
>have deep skegs, <i.e.. Broze's boats, Eddyline Falcon>, and some have a
>retractable skeg, <i.e.. Current Design Gulfstream, Valley Pintail>  and
some
>have no skeg <i.e.. Dagger RPM, Perception 3-D>
>
>The depth of this portion of the hull would then dictate the hull's
>trackability, realizing that other aspects of the hull form would also
play a
>role in the performance of said hull.


No, a skeg as defined by my dear friend Thomas Gilmer the professor of
naval Architecture at the US Naval Academy (and others) is -"A projection
from a fixed appendage applied to the underwater hull, generally to
increase the lateral area and give increased swing damping and dynamic
lateral stability to the hull. A skeg is usually of large lateral area
compared to its transverse thickness, is usually fitted in the vertical
plane, and is in the after part of the vessel."

 Why the distinction? To define clearly the difference between a boat with
steep deadrise aft and a boat fitted with an appendage. Matt's boats do not
have skegs, they have a steep deadrise aft and a relatively straight keel
line aft. Naval architecture uses a precise language to enable designers to
converse clearly about complex three dimensional shapes. For example, Steve
mentions a keelson. To a naval architect a keelson is a fore and aft above
the bottom shell on either side of the keel. A kind of auxiliary keel if
you will.

I suspect that what Steve was talking about was the bottom hull profile not
the keelson. Sounds like nit picking but if you tell a shipwright to deepen
the keelson when you mean the profile you will be a bit surprised by the
result.

Cheers,
John Winters
Redwing Designs
Specialists in Human Powered Watercraft
http://home.ican.net/~735769/







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Received on Fri Dec 25 1998 - 07:57:38 PST

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